Primates

, Volume 9, Issue 4, pp 323–349 | Cite as

On the fission of troops of Japanese monkeys

I. Five Fissions and Social Changes between 1955 and 1966 in the Gagyusan Troop
  • Yoshio Furuya
Article
Received:

Abstract

The troop of Japanese monkeys at Gagyusan has undergone five fissions between 1955 and 1966. During these 12 years, a concentrated incidence of defections of monkeys belonging to a certain age group has occurred, and a discontinuity in physical strength and age between classes arose.

When members in the lower class grow up, the discontinuity in physical strength between members in the lower class and those in the upper class gradually disappears, as a result of which the boundary between the classes becomes indistinct, and the troop falls into an unstable state. In this period, fission often occurs and the number of male deserters increases. After a lapse of a certain period of time, discontinuity in age and physical strength between classes again appears, and the boundary between classes again becomes distinct, bringing about stability in the troop again. Thus, it must be said that fission, along with single desertions of males, plays a very important role as one of the mechanisms for the maintenance of class structure in a troop of Japanese monkeys.

Next, the total number of individuals who left the main troop during the five fissions reached 130. This figure is about 1.3 times the number of monkeys who died or left singly, a total of 98 during the 12 years. The size of the Gagyusan main troop never exceeded 180 individuals during the past 12 years. From this it is clear that fission has performed a function in checking the growth of the size of the main troop.

With regard to the socionomic sex ratio, fission played a major role in checking the increase in the socionomic sex ratio of the main troop by emitting more males than females.

Troop fission is a very effective mechanism for the maintenance of the main troop at Gagyusan.

Keywords

Deserter Increase Male Deserter Animal Ecology Unstable State Class Structure 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
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Copyright information

© Japan Monkey Centre 1968

Authors and Affiliations

  • Yoshio Furuya
    • 1
  1. 1.Shizuoka Women's College YadaShizuokaJapan

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